1. Field of the Invention
The present invention relates to a sensor and more particularly to a sensor used in ultrasonically monitoring the production of welds.
2. Description of the Prior Art
Automatically operating welding apparatus are being employed to an increasing degree, for example in combination with welding robots. It must be guaranteed in such apparatus that, with the assistance of an automatic regulation, the welding electrode is conducted precisely along that path where the weld or weld seam is to be produced or where the parts to be welded to one another abut.
Up to now, the above problem was resolved in that the chronological curve of the electrical welding current flowing during the welding process was monitored. For that purpose, the welding electrode had an oscillating motion impressed on it transversely to the course of the weld or weld seam.
It is known from ZIS-Mitteilungen 7/73 and from "Schweissen und Schneiden" (1980), Pages 89 through 93 for the purpose of positioning the welding electrode to couple ultrasound into the workpieces to be welded to one another, i.e. at both sides of the welding groove, and to acquire a control quantity for the follow-up of the welding electrode from the registered transit times.
In accord with U.S. Pat. No. 4,419,562, the quality of the weld produced is checked by the evaluation of ultrasound arising during the welding process. It has been found, namely, that the ultrasound amplitude is a measure for the quality of the weld. A single receiver microphone is required for the implementation of this method. Insofar as the employment of a plurality of microphones is mentioned in this patent, it is a matter of monitoring a particular surface region with a specific individual microphone of this plurality of microphones, so that continuous coverage of adjacent surface regions of the overall surface is provided on the basis of the plurality of microphones.
The published patent application to the International Patent Application WO No. 81/01 676 likewise discloses an evaluation of ultrasound to be received during welding. Follow-up of the welding electrode is the goal with this received ultrasound. The sound of the ultrasound emanating from the arc is thereby evaluated. In order to obtain different sound of this ultrasound emanating from the arc, the welding current power and/or the momentary topical position of the welding electrode is modulated or swept with respect to the welding groove or weld. This means that the welding device is specially executed for this one and/or other measure or that an existing device must be appropriately remodeled.